BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus arizonica | Arizona White Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Arizona white oak is a native shrub or medium-sized tree [21].  As a
tree, it reaches up to 60 feet (18 m) tall with a diameter up to 3.3
feet (1 m) and has an irregularly spreading crown with stout branches
[36,41,67].  The bark on older trees may be up to 1 inch (2.5 cm) thick
[21].  The thick leaves are evergreen or nearly evergreen and about 3.2
inches (8 cm) long [16,21,61].  Pistillate catkins have two to six
flowers.  The solitary or paired acorns are 0.3 to 0.8 inch (0.8-2 cm)
long [16,21,80].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Mature Arizona white oak grows slowly, averaging about 0.1 inch per year
(0.24 cm/yr) in diameter; seedlings also grow slowly [21,49].  Once
topgrowth is removed, Arizona white oak stumps sprout.  In southeastern
Arizona following top removal by cutting, Arizona white oak regeneration
consisted primarily of stump sprouts with low seedling survival [65].
Following harvest of oak woodlands in southern Arizona, a higher
percentage of Arizona white oak stumps than Emory oak stumps failed to
sprout.  Arizona white oak sprouts also grew more slowly than Emory oak
sprouts [50].
  
Acorn production in Arizona white oak is highly variable.  Large acorn
crops, up to 32,600 acorns per tree, alternate with several years of low
acorn production [21,49].  Arizona white oak can lose 1 to 65 percent of
acorns produced to vertebrates and 1 to 50 percent to invertebrates
[49].  While postdispersal acorn loss from the soil surface can be high,
68 percent of the acorns escaped predation in a 1978 Arizona oak
woodlands study.  Arizona white oak acorns had 17 to 73 percent
germination during a study in Arizona.  The acorns have no dormancy.
Most Arizona white oak acorn germination occurs within 30 days of
dropping off of the tree; the acorns are viable for about 60 days.
Germination of Arizona white oak acorns is strongly positively
correlated with moisture during the rainy season [56].  During field
trials, germination of the acorns at 3 or 6 inches (7.5-15 cm) below the
soil surface (73%) exceeded germination rates on the litter or soil
surface (17%) [56].


SITE CHARACTERISTICS : 
Arizona white oak is widespread and occurs in arroyos, canyons,
foothills, bajadas, and on rocky slopes [25,57,81].  It occurs on flat
benches and ridges or steep sideslopes with westerly to northerly
exposures [18,51,76].  Arizona white oak is found from 3,445 to 7,218
feet (1,050-2,200 m) in elevation [43,55,57,61,73].

Arizona white oak occurs in semiarid to arid climates with a bimodal
precipitation regime, mild winters, and hot summers [2,20,44].  Soils
may be shallow to deep and moderate to very fine textured, consisting of
old alluvium from mixed sedimentary, igneous, or granitic rocks
[12,55,76].  Rock cover may be more than 15 percent [18].  Soils also
may be cobbly loams that are deep and well-drained with low
water-holding capacity [56].

Arizona white oak sites are often low in productivity due to semiarid
climate and shallow, rocky, or poorly developed soils.  Arizona white
oak frequency varies within oak woodlands.  In oak woodlands of Arizona,
Arizona white oak increase from 10 percent frequency at about 5,000 feet
(1,524 m) elevation to 45 percent frequency at about 6,000 feet (1,829
m).  It decreases in frequency above 6,562 feet (2,000 m) [49].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Arizona white oak is a seral species or climax understory species in
pinyon-juniper woodlands and pine-oak forests [4,28,57,60].  Following
cabling or fire in pinyon-juniper woodlands, Arizona white oak and other
oaks begin to establish after about 4 years, during the grass and forb
stages [28,60].  Arizona white oak is a climax species in Madrean
evergreen oak and encinal woodlands.  It is a minor climax species in
Chihuahuan pine forests [38].


SEASONAL DEVELOPMENT : 
Arizona white oak flowers as new leaves emerge.  Acorns mature during
the fall (September to November) of the same year [49,56,80].  Leaves
may drop in late winter or just before new leaves emerge in the spring
[21,80].

Related categories for Species: Quercus arizonica | Arizona White Oak